CH 1 - Wine Composition & Chemistry Flashcards
What are the 5 major components of wine?
Water, alcohol, acid, sugar, phenolic compounds
Wine is a ______ blend of _______ that give its visual, olfactory and tactile characteristics
Complex, Chemicals
Where do many of the chemical compounds found in wine originate from?
The grapes. But others are created during the fermentation process through the action of yeast cells
What happens to the compounds over time as a wine ages?
The concentrations of some compounds increase as wine ages, while others decrease with time, resulting in a wine’s ever-changing character
What percentage is water in wine?
80 - 90%
Where does the water in wine come from?
Primarily from the grapes. But small amounts may be added during winemaking
What percentage is alcohol in wine?
10 - 15%
What is the primary kind of alcohol found in wine?
Ethyl alcohol or ethanol
How is ethanol produced in wine?
It is produced during fermentation
What are other types of alcohol that are in wine in smaller amounts?
Gylcerol, Methyl Alcohol (methanol), fusel alcohols (fusel oils or higher alcohols)
Ethanol is a volatile compound that evaporates easily. When wine evaporates, what does it do with the wine’s aromas?
Carries the wine’s aromas to the nose.
What sensation does alcohol create on the palate?
Weight or body
What are “tears” or “legs”?
When swirled in the glass, high levels of alcohol result in slow, thick-appearing tears or legs
What percentage of wine’s volume does acid make up?
0.5 to 0.75 %
What are the 6 principal acids found in wine?
Tartaric acid, Malic acid, Citric Acid, Lactic Acid, Acetic acid and Succinic acid
What are 4 grape acids (found in grapes)?
Tartaric Acid, Malic Acid, Citric Acid, Succinic Acid
What are the 3 fermentation acids?
Lactic Acid, Acetic Acid, Succinic Acid
What is the most prevalent acid found in grapes and wine?
Tartaric Acid
Which acid has the strongest pH and also forms solid crystals called tartrates or wine diamonds?
Tartaric Acid
What is Malic acid?
A sharp-tasting acid frequently associated with green apples
Which type of grapes are high in Malic acid?
Underripe and cool-climate grapes
Malic acid decreases as grapes ______ on the vine
Ripen
Which type of grapes are low in Malic acid?
Overripe grapes and grapes grown in hot climates
What winemaking technique can help with high Malic acid?
Malolactic fermentation
How is Citric Acid used in wine?
It is sometimes added to increase total acidity, but its distinctive citrus flavors make it generally unsuitable for quality wines.
Is Citric Acid considered a normal component of grapes?
No, it exists in such minute quantities that specialized equipment is required to measure it. It has no sensory impact on the majority of wines
How is Lactic acid created in wine?
It is not found in grapes; it is created by lactic acid bacteria, which converts Malic acid into lactic acid during malolactic fermentation. It is also created in small amounts during primary fermentation
What impact does lactic acid have on wine?
It is less intensely acidic than Malic acid, and wines tend to be softer and smoother in mouthfeel
Acetic acid is found in most types of what?
Vinegar
When is acetic acid created?
A small amount is created during fermentation
Acetic acid in higher concentrations can have what harmful effect on wine?
At higher concentrations, a chemical reaction occurs between ethanol and oxygen caused by the harmful bacteria called acetobacter.
What is acetobacter?
It is a harmful bacteria that causes a chemical reaction between ethanol and oxygen, which can make a wine unpleasant and undrinkable
What is Succinic acid?
It is a minor component of grapes and a by-product of normal alcoholic fermentation
What kind of flavor does Succinic acid have?
It has a sharp, slightly bitter and salty flavor
What is Total Acidity (TA)?
The volume of all acids in the wine
What is pH in regards to wine?
The pH level of wine represents the combined chemical strength of the acids present
What are the typical levels of pH in wine? Which is considered high and low?
Wine measures between 2.9 (stronger) and 3.9 (less acidic)
How much sugar do grapes normally contain?
Contain 15 - 28% at harvest
What are the 2 sugars found in grapes at harvest?
Glucose, Fructose
Glucose and Fructose are highly fermentable ________ commonly known as _____ _____
Monosacharides, simple sugars
What is the process for converting sugar into alcohol?
During fermentation, yeast converts these sugars into ethanol, turning grape juice into wine. If yeast is able to finish its job, the wine will be fermented to dryness
Wines that have less sugar than a person can taste as are described as?
Dry
What are the levels of sweetness in wine?
Off-dry (medium-dry), medium sweet or sweet
A small amount of sweetness can be added to balance what in wine?
To balance high acidity
What phenolic compound give red wine its color?
Anthocyanins
What is the color range for Antocyanins?
From blue, to purple, to red
The _____ acidic wines appear ______ in hue
More, redder
The _____ acidic wines appear _____ in hue
Less, bluer
What phenolic compound gives the yellow pigments to white wines?
Flavonals
White wines from sunnier climates have a more ______ color than white wines from cooler climates
Golden
What phenolic compound is found in the skins, seeds and stems of the grapes?
Tannins
Where else are tannins found?
In oak and oak barrels
What sensations does tannins create in the mouth?
They create the textural, drying sensation in the mouth
What phenolic compound is found in oak?
Vanillin
What phenolic compound has beneficial health effects in humans?
Reservatrol
Where are the majority of phenolic compounds concentrated?
In the skin and seeds
Why are red wines richer in phenolic compounds?
Because red wines are fermented in contact with the grape seeds and skins
Which phenolic compounds polymerize or combine into longer molecule chains that become too heavy to stay suspended in the liquid and drop to the bottom as sediment?
Tannins and pigments
The production in wine has what effect on the wine?
The wine is lighter in color and less astringent
What are oxidized alcohols called that form when wine is exposed to air?
Aldehydes
Which wines are made in an oxidized manner?
Sherry and Medeira
What is the term when a wine has been encouraged to develop aldehydes?
Maderized
What is the most common form of aldehyde found in wine?
Acetaldehyde
What form of alcohol has been oxidized when acetaldehyde is created?
Ethanol
What type of wine does Acetaldehyde give its distinctive aroma to?
Sherries
What compound is molecules that result from the joining of an acid and an alcohol?
Esters
What is one of the most common Esters found in wine?
Ethyl acetate
What acid and alcohol combine in creating the ester Ethyl acetate?
Acetic acid and Ethanol
At low concentrations, what aromas does Ethyl acetate impart on wine? At high concentrations?
Fruity, flowery aroma; faulty aromas of nail polish remover, varnish or glue
What dissolved gas promotes the chemical reaction called oxidation?
Oxygen
What gets added during the winemaking process in order to absorb free oxygen molecules?
Sulfur
What dissolved gas is also found in wine and is a natural by-product of fermentation?
Carbon dioxide
What chemical compound is added to wine to keep them stable after fermentation?
Sulfites
What chemical is also a natural byproduct of fermentation and found in minute quantities?
Sulfur
In the US, if a wine contains more than _____ ppm of sulfur dioxide, a label saying “Contains Sulfites” is required
10
Highly volatile acid, often found in vingegar
Acetic acid
Main type of potable alcohol in wine
Ethanol (Ethyl Alcohol)
An acid that tastes like green apples
Malic acid
Most prevalent acid found in both grapes and wine
Tartaric acid
Another term for tartrates
Wine diamonds (tartaric acid crystals)
Conditions that can lead to a drop in malic acid
Warm/hot climate
The ripening phase
Over-ripe grapes
Malolactic Fermentation
Acid not found in grapes, but often produced during secondary fermentation (mlf)
Lactic acid
Acid that is both a minor component of grapes, and a by-product of normal alcoholic fermentation
Succinic acid
Typical range of pH for most wines
2.9 to 3,9
Two main fermentable sugars found in grapes
Glucose and fructose
Sugar remaining in a wine post-fermentation
Residual sugar
Compounds that give red wine its color
Anthocyanins
Yellow pigments found in white wines
Flavonols (flavones)
Sources of tannin
Seeds, skins, and stems of grapes
Oak barrels / other oak products
Compound found in red wine known for health benefits
Resveratrol
What is meant by “polymerization”
When molecules (such as tannins) combine into longer molecule chains
Oxidized alcohols
Aldehydes
Molecules that result from the joining of an acid and an alcohol
Esters
Chemical reactions resulting from dissolved oxygen
Oxidation
In the US, wines containing more than ____ ppm of sulfur dioxide must carry a warning label
10
